1. Field of the Invention
The invention relates to a high voltage amplifier and, in particular, to a bipolar high voltage, high efficiency DC amplifier.
2. Description of the Prior Art
Prior art devices for amplifying variable DC voltages to develop a high voltage output typically include a DC-to-DC inverter for producing a modulated signal on the primary winding of a step-up transformer, the secondary winding thereof being followed by a rectifier and filter. Such a device is capable of developing high voltage DC, but is limited in that the output is constrained to only one polarity (positive or negative) and the rate of change of the output is severely limited by the capacitance of the output filter in view of the load current.
Circuits have been developed that are capable of bipolar operation and demonstrate an improved rate of change of output by means of additional drive in both rise and fall directions. Note, for example, applicant's U.S. Pat. No. 3,525,936. Such circuits, however, require that a DC voltage be developed which exceeds twice the maximum output voltage of the circuit.
Through the use of photoconductor devices, inverter voltage amplifier circuits have been devised in which greater efficiency is achieved such that the maximum output of the circuit approaches the maximum DC voltage in the circuit. Such a system is the subject of applicant's U.S. Pat. No. 4,050,028. The power delivering capability of such systems, however, is constrained by the operating parameters of the photoconductors. Due to the limited availability of high power, high voltage photoconductors, the use of such systems as bipolar high voltage amplifiers has been limited.